Flow Data from Intake Valve Relocation

Here's before and after data from the same port on a stock Speedmaster SBM head, not CNC'd.

Before: OOTB stock 15/45/60/90 valve job with Ferrea 30/45 valve, 90.2% throat. No modifications to port or chamber.

After: Intake valve shifted 0.060", exhaust valve shifted 0.080". Valves sunk 0.085" to achieve 40/50/65/75/80 valve job with Ferrea 35/50 valve, 89.6% throat. Top cuts extended to 4.07" bore width. Light blending of new valve job to port and chamber. No modifications to port other than blending to new valve job.

This comparison would be more meaningful if the second valve job was identical to the first, but I was not about to go through the work of moving the valves and then ruin the work with a 15 degree top cut. Much of the flow gains seen here can be contributed to the new valve job and the wide/steep top cut, but I do believe some of the gains starting at 0.200 lift and up are due to deshrouding of the valve on the cylinder wall side. Moving the valve also creates additional port 'bias' that the stock port does not have because of the head bolt location. That should help top end flow a little.

Ultimately, the port will be enlarged (ported) and compared to a ported port with stock valve locations. Here are some of the things I'm trying to achieve and learn:
1. Gain width at the apex of the short side. Moving the valve 0.060" should allow for nearly that much additional width at the apex, if the air flow will stay attached to the pushrod wall. This should help lower velocity over the short turn and keep flow attached to the short turn (for a little longer) at higher lifts.
2. Gain port bias. Vizard is a big proponent of leaning the port to the common wall side. Moving the valve should allow for a little more bowl width and bias.
3. Deshroud the valve on the cylinder wall side.
4. Increase pushrod pinch width. If the valve is moved 0.060", the pushrod pinch could be widened by 0.030-0.040".

I realize that this is somewhat of an impractical test. Moving valves, moving spring seats and rocker arms can be a complicated and expensive endeavor. As with many of the tests that I have been running, it's all about learning something.

Nice .5 to .550 number! Curious to see what the planned work will yield... Care to show some pictures of the headwork?

Garrett Ellison said:

Nice .5 to .550 number! Curious to see what the planned work will yield... Care to show some pictures of the headwork?

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I’ll post some tomorrow. Seats were not replaced. Epoxy was used to form part of the top angle in the chamber and to form part of the throat. This is one port in a test head.

Very interesting. Thank you for doing some experimenting and publishing results.

What's the difference between this and installing a larger valve and offsetting the location by (half) the increase in diameter?

Mean416 said:

Very interesting. Thank you for doing some experimenting and publishing results.

What's the difference between this and installing a larger valve and offsetting the location by (half) the increase in diameter?

Click to expand...

No difference. This is just the first step - move the valve centerlines. I've been trying to find the flow limits of a 2.02 valve, so I want to stay at that size for a while. The exhaust valve was moved more than the intake in the hopes of testing something larger than a 2.08 at some point in the future.

Garrett Ellison said:

Nice .5 to .550 number! Curious to see what the planned work will yield... Care to show some pictures of the headwork?

Click to expand...

Here's a few pics. Since the new valve job is not centered on the old seat insert, it's a little confusing to look at since each angled cut goes in and out of epoxy, aluminum and insert. Hopefully the color coding helps identify each cut. Cuts are 40/50/65/75/80 with the 80 blended. The red is the 50 degree seat.

The old brass guides were removed and two new 0.687" holes drilled off center. A custom 0.689" brass guide was turned and then the end that protrudes into the port was machined to match the diameter/shape of the original guides.

Earlie A said:

Here's a few pics. Since the new valve job is not centered on the old seat insert, it's a little confusing to look at since each angled cut goes in and out of epoxy, aluminum and insert. Hopefully the color coding helps identify each cut. Cuts are 40/50/65/75/80 with the 80 blended. The red is the 50 degree seat.

The old brass guides were removed and two new 0.687" holes drilled off center. A custom 0.689" brass guide was turned and then the end that protrudes into the port was machined to match the diameter/shape of the original guides.
View attachment 1716239640View attachment 1716239641View attachment 1716239642View attachment 1716239643

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I love that nice top cut. Have you flowed your ports backwards??

I ask because it’s hard to see in the pictures what the cuts under the seat look like.

I’ve seen certain valve jobs with that many cuts act like a radius. That makes it flow much more in reverse and that’s a power killer.

What cutter are you using?

I have never flown a port backwards. I’m not saying you are wrong, but I heard Darin Morgan say to fight reversion with velocity and cam timing, not seat angles. I do know this. The steeper top cuts fight reversion both on overlap and the short side reversion that occurs at high intake valve lift.

Seat is 0.050 wide. 65 cut is 0.110. Width of 75 degree cut varies as can be seen with the purple line length. As you can imagine, the undercuts hit much harder on the exhaust valve side than on the cyl wall side. I like the way this leads the air into the combustion chamber.

All cutters are Goodson 3D system. Angles are individual cutters since all this is experimental. It’s just easier that way. I did make a custom cutter for the top cut that is a 40 degree that transitions to a 90 degree with a 4mm radius. This cuts the 40 degree all the way out to the 90 degree at the 4.07 bore circle in one cut.

Earlie A said:

I have never flown a port backwards. I’m not saying you are wrong, but I heard Darin Morgan say to fight reversion with velocity and cam timing, not seat angles. I do know this. The steeper top cuts fight reversion both on overlap and the short side reversion that occurs at high intake valve lift.

Seat is 0.050 wide. 65 cut is 0.110. Width of 75 degree cut varies as can be seen with the purple line length. As you can imagine, the undercuts hit much harder on the exhaust valve side than on the cyl wall side. I like the way this leads the air into the combustion chamber.

All cutters are Goodson 3D system. Angles are individual cutters since all this is experimental. It’s just easier that way. I did make a custom cutter for the top cut that is a 40 degree that transitions to a 90 degree with a 4mm radius. This cuts the 40 degree all the way out to the 90 degree at the 4.07 bore circle in one cut.

Click to expand...

That’s why following one man’s opinions as gospel is bad policy.

Larry Meaux says he flows his heads backwards. How do you know what the port will be like for reversion if you don’t flow the port backwards?

I’ve seen heads that flowed big numbers and they didn’t make power. I flowed them backwards and guess what? It flowed about 85% in reverse. That’s pretty high.

Once you see that you can fix it. And of course we aren’t working with the same heads he is. There is only so much you can do with the ports you are working on.

Just about anything that stops reverse flow even if it hurts forward flow will make more power.

If you don’t flow the port backwards how do you know?

Same with the exhaust. Some Chevy ports will flow in both directions at the same time. That hurts power.

Curtiss Boggs just did an interview and most of what he said aligns with my testing and not the orthodoxy I’ve heard for 40 plus years.

Newbomb Turk said:

That’s why following one man’s opinions as gospel is bad policy.

Larry Meaux says he flows his heads backwards. How do you know what the port will be like for reversion if you don’t flow the port backwards?

I’ve seen heads that flowed big numbers and they didn’t make power. I flowed them backwards and guess what? It flowed about 85% in reverse. That’s pretty high.

Once you see that you can fix it. And of course we aren’t working with the same heads he is. There is only so much you can do with the ports you are working on.

Just about anything that stops reverse flow even if it hurts forward flow will make more power.

If you don’t flow the port backwards how do you know?

Same with the exhaust. Some Chevy ports will flow in both directions at the same time. That hurts power.

Curtiss Boggs just did an interview and most of what he said aligns with my testing and not the orthodoxy I’ve heard for 40 plus years.

Click to expand...

Point taken, but not necessarily agreed with. I do appreciate having my thinking challenged. It's how we learn new things.

Now here's why I say I don't necessarily agree. I am thinking street head which means less overlap. A 50 degree seat will help prevent reversion. A 40 degree top cut will really help prevent reversion, especially if we compare it to a OOTB Edelbrock with their crazy 0 degree top cut. With the intake and exhaust valves sunk in their individual 'cones' there will be almost no line of site between the two. So in my way of thinking even if they do flow well in reverse (which I do not expect) I would not do anything to try to hurt forward flow just to prevent reverse flow. But I will admit, that just may be my current level of understanding. It changes all the time. I'm open to learning new things, but I usually need proof.

I really do appreciate the input. I'm here to learn and share, not argue. I hope that comes across in my 'tone'.

Earlie A said:

Point taken, but not necessarily agreed with. I do appreciate having my thinking challenged. It's how we learn new things.

Now here's why I say I don't necessarily agree. I am thinking street head which means less overlap. A 50 degree seat will help prevent reversion. A 40 degree top cut will really help prevent reversion, especially if we compare it to a OOTB Edelbrock with their crazy 0 degree top cut. With the intake and exhaust valves sunk in their individual 'cones' there will be almost no line of site between the two. So in my way of thinking even if they do flow well in reverse (which I do not expect) I would not do anything to try to hurt forward flow just to prevent reverse flow. But I will admit, that just may be my current level of understanding. It changes all the time. I'm open to learning new things, but I usually need proof.

I really do appreciate the input. I'm here to learn and share, not argue. I hope that comes across in my 'tone'.

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You can’t have proof of anything unless YOU test it. That’s my point. Just because I say it or Morgan says it doesn’t mean it’s gospel.

Darin and I don’t agree on several areas. One being when to use a 50 degree seat. I use them on anything I can and I’ve never lost power doing it. He says if you don’t have some arbitrary lift number they lose power. My testing (and others have tested it too) and that’s not the results we found.

If you think that hurting a flow number on the bench is bad, you’ll end up with oversized ports. Bigger holes always flow better.

I’ve said it before but the Stage VI head requires porting that is “wrong” by most every account.

I have a customer that his Stage VI heads made more power than his B1’s. On the dyno and at the track.

Then I did his B1’s and that was the first single 4 I did that went over 1k, and they used 20w50 oil (that killed probably 15, maybe 20 horsepower right there) and the plugs said it was dead fat.

The point is don’t fall in love with flow numbers. Flow and test anything you can. Raise and lower the test pressure.

Way more learning and useful information from that than just flowing a port.

Newbomb Turk said:

You can’t have proof of anything unless YOU test it. That’s my point. Just because I say it or Morgan says it doesn’t mean it’s gospel.

Darin and I don’t agree on several areas. One being when to use a 50 degree seat. I use them on anything I can and I’ve never lost power doing it. He says if you don’t have some arbitrary lift number they lose power. My testing (and others have tested it too) and that’s not the results we found.

If you think that hurting a flow number on the bench is bad, you’ll end up with oversized ports. Bigger holes always flow better.

I’ve said it before but the Stage VI head requires porting that is “wrong” by most every account.

I have a customer that his Stage VI heads made more power than his B1’s. On the dyno and at the track.

Then I did his B1’s and that was the first single 4 I did that went over 1k, and they used 20w50 oil (that killed probably 15, maybe 20 horsepower right there) and the plugs said it was dead fat.

The point is don’t fall in love with flow numbers. Flow and test anything you can. Raise and lower the test pressure.

Way more learning and useful information from that than just flowing a port.

Click to expand...

Maybe this is the source of some confusion. I have stated several times that I am trying to find the flow limits of a 2.02 valve. But that is not the same as saying I believe more flow is always better. I'm trying to understand what exactly is going on the the port that stops flow at the 305-310 cfm range. Why can't it go higher? It's about understanding the limits and what is really happening.

For example, if someone says the port won't flow more because of a lack of area at the apex, then I would say "why?" If the answer is because the velocity gets to high I would ask "so what?" If the answer is it leads to flow separation then I would ask "where?" and "how do we fix that local problem?"

My point is it looks like I'm chasing flow, but I'm really chasing understanding.

I totally agree that flow can increase and power go down. I have never disputed that. Think about this. If I was chasing flow only, I might be using the 45 degree seat. I also would not be using a 2.02 valve. I'm interested in efficiency and to some extent the coefficient of discharge. If a 2.02 valve can be made to flow what a 2.055 valve would normally flow, it should be more efficient, have higher velocities around the valve perimeter and give better fuel distribution throughout the chamber. I have spent hours with velocity probes both in the port and in the chamber. That's searching for the right shape and trying to reduce gradients, not just increase flow.

As I said, I appreciate the input. I'm sure I'll play around with reverse flow at some point. I'm sure I'll learn something.